The present invention relates to a stabilizer arrangement for a chassis of a motor vehicle, to an actuator of the stabilizer arrangement, and to a transmission which is particularly suitable for use in an actuator of a stabilizer arrangement.
It is known from prior art that so-called active stabilizer arrangements are provided on vertically movable wheel suspensions of a motor vehicle chassis. It is the object of these stabilizer arrangements to reduce rolling movements about the longitudinal vehicle axis which occur during cornering as a result of the lateral acceleration. For this purpose, two wheel suspensions pertaining to a vehicle axle are connected with one another by a stabilizer arrangement which is driven by an actuator. During the operation, a rotating movement of the stabilizer halves in the opposite direction is generated by the actuator and is transmitted by way of coupling rods to two levers or crank arms linked to one wheel suspension respectively. As a result, a compensation of the rolling movement of the vehicle body occurring during a cornering can be achieved.
The occurring load naturally takes place in opposite directions in the case of left-hand and right-hand turns. When the stabilization direction is changed, the torque of the actuator is therefore also required to be in the reversed direction. During this load change from one to the other load position, noises are generated by the play in the radial and axial direction. The change of the load positions always takes place in an area of a center position between the load positions. In the center position, the stabilizer and therefore also the transmission are almost free of torques. This change of load positions causes a change of the contact surfaces. As a result of the impacting or striking contact which occurs during a change of contact surfaces, a disturbing noise is generated. Since, when driving straight ahead or along slight bends, the actuator is always situated in this area of the neutral position, load changes and resulting noises occur frequently. In addition to the noises, this also results in increased wear of the contact areas.
German Patent Document DE 44 43 809 A1 discloses the use of a hydraulic actuator, which has idling losses, for generating the rotating movement of the stabilizer halves in opposite directions. For reducing the stress caused by noise, the two stabilizer halves are glued to the actuator, and a bearing of the stabilizer halves in rubber metal bearings is suggested for noise reduction and vibration damping.
Unpublished German Patent Application DE 100 02 455 describes an actuator for a stabilizer arrangement which is clearly simplified in comparison to known solutions. For forming an actuator, a transmission is connected with a drive in the form of an electric-motor actuating drive, a hydraulic cylinder piston unit or a similar device. Based on the recognition that a transmission in a stabilizer arrangement must be able to adjust an angle of rotation of maximally approximately 45°, this patent application discloses the use of curved-path transmissions. For adjusting an angle of rotation, a coupling element is guided simultaneously in different curved paths of two separate curved-path carriers along a common longitudinal axis. An axial displacement of the coupling element is caused, for example, by an electric-motor-driven threaded spindle, so that rotating movements of the curved-path carriers with respect to one another can be achieved in a simple and reliable manner. The rotating movements are transmitted to the respective wheel suspensions by way of the stabilizer halves which are non-rotatably mounted in each case on one curved-path carrier.
Based on a transmission and an actuator of the above-described stabilizer arrangement, it is an object of the present invention to reduce the noise caused by its operation.
According to the invention, this object is achieved by the embodiments of the present invention as described and claimed hereinafter.
A stabilizer arrangement according to the invention is therefore characterized by an actuator having a curved-path transmission in which a coupling element of the transmission has at least one element engaging in the curved paths of the curved-path carrier. The element is acted upon by prestressing such that, in an essentially unloaded neutral position of the transmission, it rests against a curved path of each of the curved-path carriers. By setting a static prestress, for example, between a drive of the actuator and the coupling element mechanically connected to the drive, the engaging element can securely rest against a curved path for each curved-path carrier, even in a neutral position.
In a preferred embodiment of the invention, at least two elements are arranged to engage two different curved paths of curved-paths carriers, and devices are provided for the spring-elastic bracing of the two engaging elements. The two engaging elements may be arranged on a common shaft, in which case the shaft includes, for example, a spring elastic material, particularly a spring steel. The shaft, made of a spring-elastic material, is preferably prestressed by a deviation from a linear connection between the two engaging elements. As an alternative or in addition, the paths of two opposite curved paths can be arranged to be mutually offset by a defined amount for generating a prestress in the shaft.
In a further embodiment, a spring-elastically constructed narrowing and/or a spring element is provided at least in the area of a neutral position on a path or flank of a curved path. In this case, the term path or flank of a curved path is the shape or line of an edge of a curved path which has a recess, a undercut, or a filling by a suitable other material, for example, by a rubber-type material, for forming a spring-elastic area according to the invention.
In an advantageous further development, a transmission according to the invention has at least two shafts with the engaging elements at the coupling element and correspondingly several complementary curved paths in the separate curved-path carriers. This creates several loading points by which the respective loading is reduced. Furthermore, in the layout, symmetries of the loading and a comparatively more favorable course of torques can be utilized in order to, for example, be able to lower the strength of the individual structural elements and/or use cost-effective materials. Thus, while the costs are lowered and the service life is increased, on the whole, a favorable course of torques is obtained in the curved-path carriers as well as in the coupling element.
In an embodiment, spring elements are arranged on the above-mentioned shaft and/or between the above-mentioned shafts for generating a prestress. Depending on the required rigidity of the spring, these may be simple coil springs constructed as tension and/or pressure springs. The shafts may, in addition, be linked to the coupling element. In other words, the shafts carrying the engaging elements are at least slightly movable with respect to the coupling element, particularly in a rotatable or swivellable manner, specifically with respect to one another with the effect of the spring element or elements.
For a significant reduction of the resistance or of the friction during the displacement of the coupling element under load, the element engaging in the curved path is constructed as a roller or a pair of rollers. Among other things, a concrete structural shape of the respective transmission should be taken into account here, particularly whether a series mounting or a superposing of the curved-path carriers is involved. These different structural shapes also are indicated in the above-mentioned non-published German Patent Application No. 100 02 455.6. When selecting the material pairings of roller material and the material of the curved paths in the contact area, under the condition of the transmission of predetermined torques while the frequency of the occurrence is statistically determined, the person skilled in the art can freely employ known materials and finished products, particularly in the area of the rollers as well as their bearing.
In a preferred embodiment of the invention, the engaging elements are braced with respect to one another such that each engaging element rests at least in the area of a neutral position against a side or flank of the path or curved path. This solution is provided particularly for the mutual bracing of the engaging elements of a spring-elastically constructed, mutually eccentrically arranged bearing of the engaging elements on a common end of the shaft. In order to generally prevent a lifting of the rollers off a respective curved path, a constant contact of the rollers on the curved paths can also be achieved by adjusting the prestress.
In a preferred embodiment of the invention, a driving unit comprises a threaded spindle on which the coupling element of an above-described transmission is axially displaceably arranged as a nut. In this case, the driving unit may be very cost-effectively constructed as an electric motor.
A transmission according to the present invention, while maintaining its above-mentioned advantages, may also be adapted in a simple manner to a use in other technical fields with corresponding problems outside the vehicle construction field.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.